Non destructive quench of bulk YBaCuO in liquid argon

The superconducting fault current limiter (FCL) is particularly attractive since no conventional limiting device exists for high voltage networks and thus corresponds to a real need. YBCO is a good candidate for current limit ation due to its large critical current density and its large normal state electric field. This material is, however, very sensitive to hot spots in l iquid nitrogen. An operation at higher temperatures decreases the critical current density and consequently reduces local heating (hot spots). Tests i n liquid argon (87.3 K) were carried out. The critical current density rema ined large (about 50 MAm-2, 0 T). For instance the limiting current is much higher (11-15 times) than the critical current but to our knowledge, it is the first time that a cion destructive quench was observed in bulk YBCO mo no-domain sample. The power and energy per unit volume developed during the transition reached 75 GWm(-3) and 350 MJm(-3) respectively. These values a re large enough to induce an effective current limitation and weak enough t o restrict overheating and resulting destruction. In this paper we report m easurements and their analysis and show a new and hopeful way to improve YB CO limitation efficiency. (C) 1999 Elsevier Science Ltd. All rights reserve d.